In one form of electric arc welding apparatus in common use at present, a flexible electrode wire coiled in a supply reel rotatably mounted on a cantilever supported shaft is fed off the reel by feed rolls to the welding head of the apparatus. The support shaft with the wire supply reel thereon are both enclosed within a housing which is provided with a pivoted overhead and/or side door that can be swung out of the way to permit the axial sliding of the reel onto and off the free end of the cantilever supported shaft. Owing to the normally appreciable size and weight of a reel with a full supply of electrode wire coiled thereon, a sturdy support must be provided for the supported end of the cantilever mounted shaft, and the swing door must be of corresponding appreciable and cumbersome size.
To prevent overrunning of the rotated reel upon each stoppage of the feeding of the electrode wire off the reel by the feed rolls, with resulting unwinding of a portion of the remaining coiled wire from the reel and possible displacement of such unwound wire portion off the sides of the reel, the reel supporting shaft in such prior forms of electric arc welding apparatus have been customarily provided with a manually adjustable spring controlled friction brake means for frictionally engaging shoe elements incorporated in the shaft with the inside wall of the hub portion of the reel to thereby exert a frictional drag braking action thereon during the rotation of the reel by the electrode wire drawn off therefrom by the feed rolls. Because of the higher rotational inertia of a reel with a fuller supply of coiled wire thereon, more brake force is required to be applied thereto to prevent overrunning of the reel, on each stoppage of the feeding of the electrode wire off the reel by the wire feed rolls, than is required to prevent overrunning of a reel with a reduced wire coil diameter. This then results in a higher wire feed force being applied to the coiled wire on the reel as the wire coil diameter reduces.
With such prior cantilever shaft supported electrode wire reel support arrangements, moreover, the replacement of an emptied reel by one containing a full supply of electrode wire coiled thereon becomes a rather complicated and time consuming operation. To replace an emptied reel, the closed door of the housing must first be swung to its open position to permit sliding movement of the emptied reel endwise off the free end of the cantilever supported reel mounting shaft, after which the fastening means, such as threaded end cap or fastening nut holding the reel in place on the shaft, must then be removed to free the emptied reel for sliding movement endwise off the free end of the support shaft. After sliding of a replacement reel containing a further supply of electrode wire onto the support shaft into proper position thereon, the replacement reel must then be fastened in place on the shaft and the closure door then swung back to its closed position. Thus, it will be appreciated that the replacement of an emptied electrode wire supply reel by one containing a new supply of electrode wire becomes a rather involved and time consuming operation.